1. Field of the Invention
The present invention relates to a liquid crystal display. In more detail, the present invention relates to a liquid crystal display capable of solving a problem of light leakage occurring after the storage in a high-humidity environment which is an emerging problem in a liquid crystal display for which a thin glass substrate having a thickness of 0.5 mm or less is used.
2. Description of the Related Art
A liquid crystal display is a space-saving image display with small power consumption, and its application is widening every year. In the past, liquid crystal displays had a serious defect of a large viewing angle dependency of a displayed image, but a wide viewing angle liquid crystal mode such as a VA mode or an IPS mode has been put into practical use, and accordingly, the demand of the liquid crystal displays is rapidly expanding even in a market requiring a high-quality image such as a television.
In a basic configuration of the liquid crystal display, polarization plates are provided on both sides of a liquid crystal cell. The polarization plate passes only light on a plane of polarization in a certain direction, and the performance of the polarization plate is a key determinant of the performance of the liquid crystal display. The VA mode or the IPS mode is used in a normally black (black is displayed when the voltage between electrodes in the liquid crystal cell is zero) state, and, at this time, the light absorption axes of the polarization plates on both sides of the liquid crystal cell are disposed so as to be orthogonal to each other. Out of non-polarized light emitted from a light source, only polarized light in a certain direction passes through the polarization plate on the light source side, maintains the polarization state when passing through the liquid crystal cell, and is absorbed by the polarization plate on a viewing side having the light absorption axis disposed orthogonal to the polarization plate on the light source side. Then, black displaying can be realized.
The polarization plate in a liquid crystal display has a configuration in which, generally, transparent protective films are attached to the front and back sides of a polarizer made of a polyvinyl alcohol film or the like in which iodine or a dye is adsorbed and oriented. As the polarization plate protective film, a cellulose acylate-based polarization plate protective film represented by cellulose acetate has been widely used since the cellulose acylate-based polarization plate protective film has high transparency and is capable of easily ensuring adhesiveness to polyvinyl alcohol which is used for the polarizer.
Meanwhile, in recent years, an acryl resin has been more frequently used as the polarization plate protective film. This is because the attachment technique has improved, and it has become possible to ensure adhesiveness to a polyvinyl alcohol.
In recent years, as the application of the liquid crystal display has been expanding, there has been a demand for a larger size and a higher-quality texture in the liquid crystal display. To reduce the weight of the enlarged liquid crystal display, the thicknesses of a variety of members have been decreased, and particularly, the thickness of a glass substrate has been decreased from the thickness of the related art of 0.7 mm to 0.5 mm. In addition, recently, studies are underway regarding a 0.3 mm-thick glass substrate. Furthermore, there is a portion corresponding to the frame, which is called a bezel, in the peripheral portion of a screen, and the width of the bezel is becoming narrower to produce a higher-quality texture.
In JP2002-6133A and JP2003-84136A, studies are made regarding uneven colors or fading occurring when a polarization plate is placed in a high-temperature environment, and it is disclosed that uneven colors can be improved by decreasing the contractive force in a polarizer configuring a polarization plate. However, in these documents, there is a proposal for improving the uneven colors in a polarization plate placed for a short period of time in a high-temperature environment, but no attention is paid to a problem of the occurrence of unevenness (light leakage at four corners of a panel: hereinafter, also referred to as “warp”) based on the warpage of the panel caused when a liquid crystal display in which a liquid crystal cell having a glass thickness of 0.5 mm or less is used has been placed in a high-temperature environment for a long period of time.